Trinidad Express 1 Dec 10;
Mass coral bleaching as a result of unusually warm sea surface threatens the coral reefs of Tobago. The health and very survival of coral reefs around Tobago is currently under threat from widespread devastation in what is now looking to be the worst mass coral bleaching event the island has ever witnessed.
Coral bleaching is a phenomenon that corals display in particularly stressful conditions, such as unusually high sea-water temperatures. The algae that provide the coral with food and live within its tissue are expelled from the living coral animal. As a result, the coral tissue loses its colouration and appears white; commonly referred to as coral bleaching. The algae provide up to 90 per cent of the food to the coral and if they are not regained in a matter of weeks, the coral is likely to die from starvation.
In 2005, unusually high sea surface temperatures caused widespread mortality of reef animals and a reduction of hard coral cover on many reefs around the island including Buccoo Reef, one of Tobago’s main tourist attractions, renowned for its vibrant and colourful reefs. A mass-bleaching event is currently unfolding in the Caribbean with island nations in the Lesser Antilles including Tobago experiencing the highest sea surface temperatures. Many of the popular reefs in Tobago now resemble winter snow scenery. The Caribbean has been warmer than average since January and temperatures in Speyside have been high enough to initiate bleaching (29.5°C for the southern Caribbean) for nearly 2 months according to temperature logger data. Conditions are considered even more stressful than 2005 in terms of sustained higher temperatures.
During the 2005 mass-bleaching event, Speyside remained relatively unaffected. It is likely that the strong local currents carried away the warmer temperatures and sediment from the Orinoco River. Unfortunately, Speyside has not been so lucky this year as it has suffered extensive bleaching which researchers believe may be related to the high temperatures combined with the seasonal pulse of freshwater from the Orinoco River in Venezuela.
The reefs around Tobago have been monitored since the last mass-bleaching event in 2005. Coral Cay Conservation, a UK-based not for profit organisation, has been mapping the reefs of Tobago since 2007. They are currently working with the Speyside Eco-Marine Park rangers to monitor the extent, recovery and mortality of reefs in the areas of Speyside and Charlotteville.
In addition to the high water temperatures, Tobago has also been impacted by Hurricane Thomas. The resulting storm caused numerous landslides and muddy waters which have remained in Charlotteville bay for over three weeks.
If coral reefs recover they still remain vulnerable to disease and other environmental stressors, such as these storms. After the last bleaching event in 2005, many coral became infected with yellow blotch disease and white plague. We are now already beginning to see a number of coral diseases.
Severe landslides and muddy waters affected Charlotteville following Hurricane Thomas. Bleached coral suffering from black band disease and white plague disease in Speyside.
Being a small tropical island, it is no secret that Tobago heavily relies on tourism as one of its main sources of income and coral reef related activities make up a big part of this income. If reefs fail to recover from this bleaching event, we are looking at a replacement of from thriving coral reefs with abundant life to baron seascapes dominated by seaweed. Fishermen can expect to be spending more hours at sea to catch fewer fish if the correct action is not taken now. In the event that the island’s reefs should disappear, it will have severe implications for the economic benefits derived from these natural resources, estimated to constitute nearly half of Tobago’s GDP according to a economic valuation conducted by the World Resource Institute in 20061.
Successful recovery of the coral reefs of Tobago depends on a number of factors including:
1) The presence of other healthy reefs where new coral larvae can be sourced and generated, replenishing damaged reefs.
2) Effective sewage treatment so that chemicals that promote algae overgrowth and coral diseases do not wash onto the reefs.
3) Stopping upland deforestation and poorly planned coastal construction projects that result
